Hair cutting machine having a vibrating armature drive



Aug. 14, 1956 W. RoLLl ET AL 2,759,114

CHINE HAVING A VIBRATING ARMATURE DRIVE HAIR CUTTING MA l Filed July 22,1952 /NVEN TOR S.

, HERBERT HAUSRATH KLEVT WENDE L RoLLl AND ERICH BY.'

United States Patent HAIR CUTTING MACHINE, HAVING A. VIBRATING ARMATUREDRIVE Wendel Rolli, Stuttgart-Degerloch, Herbert Hausrath, Karlsruhe,and Erich Klett, Stuttgart-Bad Canstatt, Germany, assignors to RobertBosch G. m. b. H., Stuttgart, Germany Application July 22, 1952,I SerialNo., 300,248 Claims priority, application Germany August 10, 1951Claims. (Cl. 310-29) The present invention relates to a hair cuttingmachine having an electromagnetic drive including a vibrating armaturewhich is periodically attracted by an electromagnet excited byalternating current.

Constructions of hair cutting machines are already known in which thearmature of the drive magnet is fixed to a leaf spring or the like, ispolarised by means of a permanent magnet, and swings to and fro betweenthe pole shoes of an electromagnet. Despite a considerable power intakesuch arrangements are only capable of iniparting a small driving powerto a cutter head. Theref ore it has already been attempted by Variousways and means to combine the oscillating parts of the cutter head withswinging armature systems whose natural frequency coincides with theexciter frequency of the electromagnet. But those measures were onlysatisfactory to. a small extent.

The present invention is based on the knowledge that in the knownarrangements the electromagnetic tractive forces are. unfavourablyrelated to the actual position of the oscillating armature, because theforces reach. their maximum value just at that time when the armature isclosest to the electromagnet and the cutting blade 0f: the cutter headhas reached one extremity of its traveh i. e. a point, on its track atwhich it reverses.v An arrange,- ment correspondingy to the kineticprinciples would therefore have to produce oppostcly acting drivingforces, especially at the aforedescribed moments, so that a phasedisplacement of 180," should exist between deflection and driving force.

This requirement has been fulfilled by the. fact that the. oscillatingarmature. in accordance with the invention rolls over a preferablyslightly curved surface during its. working movements, whereby the.lengths of. the momcntary load and the effort lever arms of the armaturevary constantly.

The. invention will be further described with reference to theaccompanying Vdrawings which show hy way of example one embodiment ofthe invention- In the drawings.:

Fig. 1 is a longitudinal section, along the lino 1.*-1 of Fig. 2., of ahair cutting machine driven by a rocking armature,

Fig. Z is. another longitudinal section along the line lI-Il of Fig. lwith the cutter head removed, and

Fig. 3 is a cross section along the line Ill-sill of Fig. l.

The driving mechanism of the hair cutting machine shown in the drawingsis housed in two handle parts. 11 and 12 of pressed material andconsists essentially of an E-shaped magnet core. 13, a laminatedoscillating or rocking armature 14 and a cranked driving arm. 155mounted on the armature. When a cutter headv 16. is attached the arm 1 5engages in a recess ouv the cutter blade. Exciter coils 20, y21 areyslipped over outer arms 17 and 18 of the magnet core 13,. The excitercoils 20 and 21 which are wound with the same number of turns and are so'disposed that on being connected to an alternating current supply in acircuit including a tumbler c ICC switch 22, they magnetise the freeends of they outer arms 17, 18 with opposite polarities.

The centre arm of the magnet core 13 includes a permanent magnet 2.4having a pole piece 19 assembled from sheet iron. The various parts ofthe magnet core, that is to say the outer arms 17 and 1 8, the portioninterconnecting them, the permanent magnet 24 and pole piece 19, areheld together by two brass plates 28 and` 29,.

When the armature 1,4 is in its central position as shown in thedrawings the permanent magnet 24' magnetises the two outer arms 17 and18 symmetrically with a permanent magnetic flux as indicated by thebroken arcuate arrowed lines in Fig'. 2. The alternating UX produced bythe exciter coils 20 and l21 is supcImPOSed on this permanent flux. Bythe suitable choice of the number of turns in the exciter coils theamplitude of the alternating flux may he so adjusted that it issubstantially or nearly equal to the magnitude of the. permanent flux.If therefore the magnetic flux in one outer arm, for example 17, owingto the current in exciter coil, for example 20, has just assumed doublethe value of the permanent flux, then the flux is substantially ornearly nil on the, other arm,I for example 1S, and the centre portion ofthe armature 1,4 rolls along the centre arm of thc magnet core which isadapted to form an arcuate rocking surface. 25', in the direction of themore extensively magnetised outer arm, for example 1,7. )n re,- versalor" the, current thrnugh the, exciter coils during the followinghalf-cyclei the magnetic, llux in` the other outer arm, `for example 1S,reaches substantially or nearly double the value of the permanent ux sothat the armature is forced to swing in the opposite. direction wherebyits central portion rolls on the arcuate surface 25 in the oppositedirection.

Arranged opposite the centre of the rocking surface are resilientpivoting means, i. e., a retaining spring `26, one end of which isinserted in a recess 27 in the casing wall 12 whilst its other endprojects in to an oppositely extending bore in the armature 14 and thussecures the armature from longitudinal displacements. The spring 26accordingly is a bearing element made of resilient material. It alsoserves the purpose of returningI the armature 14 to the centra-lposition as shown, in the event ofl the current through the excitercoils current being interrupted.

As the armature rolls the force exerted by the spring 26 increaseslinearly andk the length of the lever arm of the armature on which thespring presses in a return direction also increases approximatelylinear. Thus the moment exerted by ther spring force, in the returningdirccti'on rises steeply and, in fact, approximately quadratically. Theattractive force, exerted by the magnet system increases in accordancewith the approach. of the armature to the magnet pole in question and.in fact also increases. quadratically. In the meantime as the armaturerolls the length of the lever arm on which the magnetic f orce actsdecreases approximately linearly, so that the torque produced by themagnetic force increases more gradually than the returning momentproduced by the spring force.

In this cycle of movement of the armature the constant change ofposition of the instantaneous centre and the consequent change in lengthof load and effort arm of the armature plays an important part. As, theradius of curvature of the rolling surface 25 is considerable, itpreferably amounts to, more than 20 times the: length of the rollingsurface-the point of abutment ofthe, armature changes rapidly. Thereforea slight; approach of the armature to one of the outer arms, 17 forexample, of the magnet core is sulicient to. roll thc armature from thecentre M' of the arcuate rocking surface to for example the end A ofthis surface, whereby the length of the load arm decreases trom CM toCA, whilst on the other hand the length of the effort arm is reducedfrom BM to BA. In the embodiment shown, CM=65 mm., CA=40 mm., Bit/1:32rnm. and BA=10 mm. The ratio k of the lengths of the load and effortarms thus changes for the left half of the armature from As may beeasily seen, the length of the lever arm upon which the spring1 26presses when the armature is attracted from the central position, isinitially practically zero, but increases rapidly to AM. ln this mannerthe amature does not strike the outer pole piece if the spring 26 hasbeen suitably chosen, and yet despite this ensures a strong drivingimpulse for the cutter blade up to shortly before reaching its reversingpoint.

In a further development of the invention it is naturally possible insuch an arrangement to tune the spring pressure and the mass of theswinging parts to the frequency of the electric supply to the excitercoils. This may be achieved by so arranging the spring that it may beadjustably pre-compressed.

We claim:

1. An electro-magnetic drive for driving a cutter head in a hair cuttingmachine, including an electro-magnetic system having a core member, anarmature member and exciter coils, said core member being E-shaped andhaving two outer arms and one centre arm, said centre arm having anarcuate outer surface, resilient pivoting means, pivotally holding saidarmature in abutting contact with said arcuate surface of said centrearm while permitting displacement of the armature from a given positiontowards either of said outer arms, said exciter coils being disposed onsaid outer arms for energisation of the electro-magnetic system from analternating current electricity supply, and means to produce a permanentmagnetic ux linkage at least said centre arm.

2. An electro-magnetic drive according to claim l, said exciter coilsdisposed on said outer arms being adapted to produce instantaneouslyoppositely acting magnetic fluxes in said outer arms whereby said outerarms are magnetised in opposite directions to one another.

3. An electro-magnetic drive according to claim l, a permanent magnet insaid centre arrn for producing a permanent magnetic ux linking saidcore.

4. In a hair clipper, in combination, an elongated casing havingopposite ends each of which is formed with an opening; an E-shaped coremember supported in said casing with the arms of the E-shaped coremember extending transversely to the length of said casing, the centerarm of said E-shaped core member having a free arcuate end surface; apair of coil windings arranged respectively about the outer arms of saidE-shaped core member and adapted to be connected to a pair of energizingconductors passing through one of said openings in said casing; anelongated armature having a substantially central portion thereoflocated against said arcuate surface, and having opposite end portionsrespectively located opposite the free ends of said outer arms of saidE-shaped core member so as to define a path with said E-shaped coremember for the magnetic flux produced by the coil windings whenenergized; resilient means engaging said armature for urging the sameinto abutment with said arcuate surface of said center arm so as tocause said armature to rock on said arcuate surface in accordance withthe energization of the coil windings, the maximum travel of saidarmature towards said outer arms of said E-shaped core member beinglimited by said free arcuate end surface of said center arm; andtransmission means connected to said armature for movement therewith,extending through said other opening.

5. In a hair clipper, in combination, an elongated casing havingopposite ends each of which is formed with an opening; an E-shaped coremember supported in said casg. ing with the arms of the E-snaped coremember extending transversely to the length of said casing, the centerarm of said E-shaped core member having a free arcuate end surface andbeing longer than the outer arms of said E-shaped core member; a pair ofcoil windings arranged respectively about the outer arms of saidE-shaped core member and adapted to be connected to a pair of energizingconductors passing through one of said openings in said casing; anelongated armature having a substantially central portion thereoflocated against said arcuate surface, and having opposite end portionsrespectively located opposite the free ends of said outer arms of saidE-shaped core member so as to define a path with said E-shaped coremember for the magnetic ux produced by the coil windings when energized;resilient means engaging said armature for urging the same into abutmentwith said arcuate surface of said center arm so as to cause saidarmature to rock on said arcuate surface in accordance with theenergization of the coil windings, the maximum travel of said armaturetowards said outer arms of said E-shaped core member being limited bysaid free arcuate end surface of said center arm; and transmission meansconnected to said armature for movement therewith, extending throughsaid other opening.

6. In a hair clipper, in combination, an elongated casing havingopposite ends each of which is formed with an opening; an E-shaped coremember supported in said casing with the arms of the i-shaped coremember extending transversely to the length of said casing, the centerarm of said E-shaped core member having a free arcuate end surface whoseradius of curvature is equal to substantially ten times the peripherallength of said arcuate surface; a pair of coil windings arrangedrespectively about the outer arms of said E-shaped core member andadapted to be connected to a pair of energizing conductors passingthrough one of said openings in said casing; an elongated armaturehaving a substantially central portion thereof located against saidarcuate surface, and having opposite end portions respectively locatedopposite the free ends of said outer arms of said E-shaped core memberso as to define a path with said E-shaped core member for the magneticux produced by the coil windings when energized; resilient meansengaging said armature for urging the same into abutment with saidarcuate surface of said center arm so as to cause said armature to rockon said arcuate surface in accordance with the energization of the coilwindings, the maximum travel of said armature towards said outer arms ofsaid E-shaped core member being limited by said free arcuate end surfaceof said center arm; and transmission means connected to said armaturefor movement therewith, extending through said other opening.

7. In a hair clipper, in combination, an elongated casing havingopposite ends each of which is formed with an opening; an E-shaped coremember supported in said casing with the arms of the E-shaped coremember extending transversely to the length of said casing, the centerarm of said E-shaped core member having a free arcuate end surface andbeing longer than the outer arms of said E-shaped core member, saidarcuate end surface having a radius of curvature equal to substantiallyten times the peripheral length of said arcuate surface; a pair of coilwindings arranged respectively about the outer arms of said E-shapedcore member and adapted to be connected to a pair of energizingconductors passing through one of said openings in said casing; anelongated armature having a substantially central portion thereoflocated against said arcuate surface, and having opposite end portionsrespectively located opposite the free ends of said outer arms of saidE-shaped core member so as to define a path with said E-shaped coremember for the magnetic flux produced by the coil windings whenenergized; resilient means engaging said armature for urging the sameinto abutment with said arcuate surface of said center arm so as tocause said armature to rock on said arcuate surface` in accordance withthe energization of the coil windings, the maximum travel of saidarmature towards said cuter arms of said Efshaped` core member beinglimited by said free arcuate. end surface of said center arm; andtransmission means connected to said armature for movement therewith,extending through said other opening.

8. Iny a hair clipper, in combination, an elongated cas ing havingopposite ends each of which is formed with an opening; an E-shaped coremember supported in said casing with the arms of the Eshaped core memberexa tending transversely to the length of said casing, the center arm ofsaid E-shaped core member having a free arcuate end surface; a pair ofcoil windings arranged respectively about the outer arms of saidE-shaped core member; a pair of energizing conductors passing throughone of said openings in said casing and connected tothe coil windings,said coil windings when energized producing oppositely acting magneticiiuxes in said outer arms of said E-shaped core member so as tomagnetize said outer arms in opposite sense with respect to one another;an elongated armature having a substantially central pore tion locatedagainst said arcuate surface, and having opposite end portionsrespectively located opposite the free ends of said outer arms of saidE-shaped core meme ber so as to deline a path with said E-shaped coremem-4 ber for the magnetic flux produced by said coil windings;resilient means engaging said armature for urging the same into abutmentwith said arcuate surface of said center arm so as to cause saidarmature to rock, on said arcuate surface in accordance with theenergization of the coil windings, the maximum travel of Said armaturetowards said outer arms of said E-shaped Core member being limited bysaid free arcuate end surface of said center arm; and transmission meansconnected to said armature for movement therewith, extending throughsaid other opening.

9. In a hair clipper, in combination, an elongated casing havingopposite ends each of which is formed with, an opening; an E-shaped coremember supported in said casing with the arms of the E-shaped coremember extending transversely to the length of said casing, the centerarm of said E-shaped core member having a free arcuate end surface, aportion of said center arm being partially in the form of a permanentmagnet; a pair of coil windings arranged respectively about the outerarms of said E-shaped core member and adapted to be connected to a pairof energizing conductors passing through one of said openings in saidcasing; an elongated armature having a substantially central portionthereof located against said arcuate surface, and having opposite endportions respectively located opposite the free ends of said outer armsof said E-shaped core member so as to deine a path with said E-shapedcore member for the magnetic iiux produced by the coil windings whenenergized; resilent means engaging said armature for urging the sameinto abutment with said arcuate surface of said center arm so as tocause said armature to rock on said arcuate surface in accordance withthe energization of the coil windings, the maximum travel of saidarmature towards said outer arms of said E-shaped core member beinglimited by said free arcuate end surface of said center arm; andtransmission means connected to said armature for movement therewith,extending through said other opening.

10. In a hair clipper, in combination, an elongated casing havingopposite ends each of which is formed with an opening; an E-shaped coremember supported in said casing with the arms of the E-shaped coremember extending transversely to the length of said casing, the centerarm of said E-shaped core member having a free arcuate end surface, aportion of said center ann being partially in the form of a permanentmagnet; a pair of coil windings arranged respectively about the outerarms of said E-shaped core member; a pair of energizing conductorspassing through one ofsaid open-ings said casing and connected to thecoil windings, said coil windings when energized produce oppositeacting' magnatiel fluxes in said outer arms of said E-shaped core memberso as to magnetize said outer arms in opposite sense With respect to oneanother, the density of the magnetic ux produced by said coils beingsubstantially equal to the density of the magnetic flux produced by saidpermanent magnet; an elongated armature having a substantially centralportion located against said arcu-l ate surface, and having opposite endportions respecs tively located opposite the free ends of said outerarms of Said E-Shped core member so as to define a path with saidE-shaped core member for the magnetic flux produced by said coilwindings; resilient means engaging said armature for urging the sameinto abutment with said arcuate surface of said center arm so as tocause said armature to rock on said arcuate surface in accordance withthe energization of the coil windings; and transmis,- sion meansconnected to said armature for movement therewith., extending throughsaid other opening.

il. In a hair clipper, in combination, an elongated casing havingopposite ends each of which is formed with an opening; an E-shaped coremember supported in said casing with the arms of the E-shaped coremember ex tending transversely to the lengthof said casing, the centerarm of; said E-shaped core member having a free arcuate end surface andbeing longer than the outer arms of said Efshaped core member, a portionof said center arm being partially in the form of a permanent magnet; a.pair of coil windings arranged respectively about the outer arms of saidE-shaped core member and adapted to be connected to a pair of energizingconductors passingthreugli one. ot said openings in. Said. Casing; anelongated armature having a substantially central portion thereoflocated against said arcuate surface, and having opposite end portionsrespectively located opposite the free. ends of said outer arms of saidE-shaped core mem. ber so as to define a path with said Eeshaped coremem= ber for the magnetic flux produced by the coil windings whenenergized; resilient means engaging said armature for urging the sameinto abutment with said arcuate surface of said center arm so as tocause said armature to rock on said arcuate surface in accordance withthe energization of the coil windings, the maximum travel of saidarmature towards said outer arms of said E- shaped core member beinglimited by said free arcuate end surface of said center arm; andtransmission means connected to said armature for movement therewith,extending through said other opening.

lZ. In a hair clipper, in combination, an elongated casing havingopposite ends each of which is formed with an opening; an le-shaped coremember supported in said casing with the arms of the E-shaped coremember extending transversely to the length of said casing, the centerarm of said E-shaped core member having a free arcuate end surface, aportion of said center' arm being partially in the form of a permanentmagnet, said center arm being longer than the outer arms of saidE-shaped core member; a pair of coil windings arranged respectivelyabout the outer arms of said E-shaped core member; a pair of energizingconductors passing through one of said openings in said casing andconnected to the coil windings, said coil windings when energizedproduce opposite acting magnetic fluxes in said outer arms of saidE-shaped core member so as to magnetize said outer arms in oppositesense with respect to one another, the density of the magnetic fluxproduced by said coils being substantially equal to the density of themagnetic flux produced by said permanent magnet; an elongated armaturehaving a substantially central portion located against said arcuatesurface, and having opposite end portions respectively located oppositethe free ends of said outer arms of said E-shaped core member so as todefine a path with said E-shaped core member for the magnetic iiuxproduced by said coil windings; resilient means engaging said armaturefor urging the same into abutment with said arcuate surface of saidcenter arm so as to cause said armature to rock on said arcuate surfacein accordance with the energization of the coil windings, the maximumtravel of said armature towards said outer arms of said E-shaped coremember being limited by said free arcuate end surface of said centerarm; and transmission means connected to said armature for movementtherewith, extending through said other opening.

13. in a hair clipper, in combination, an elongated casing havingopposite ends each of which is formed with an opening; an E-shaped coremember supported in said casing with the arms of the E-shaped coremember extending transversely to the length of said casing, the centerarm of said E-shaped core member having a free end surface; a pair ofcoil windings arranged respectively about the outer arms of saidE-shaped core member and adapted to be connected to a pair of energizingconductors passing through one of said openings in said casing; anelongated armature having a substantially central surface thereoflocated against said free end surface of said E-shaped core member, oneof said surfaces being arcuate, said armature having opposite endportions respectively located opposite the free end portions of saidcuter arms of said E-shaped core member so as to define a path with saidE-shaped core member for the magnetic flux produced by the coil windingsWhen energized; resilient means engaging said armature for urging thesame into abutment with the free end surface of said center arm so as tocause said armature to rock on the arcuate surface in accordance withthe energization of the coil windings, the maximum travel of saidarmature towards said outer arms of said E-shaped core member beinglimited by said free end surface of said center arm; and transmissionmeans connected to said armature for movement therewith, extendingthrough said other opening.

14. An electromagnetic drive for driving a cutter head in a hair cuttingmachine, including an electromagnetic system having a core member, anarmature member and exciter coils, said core member being E-shaped andhaving two outer arms and one center arm, a permanent magnet in saidcenter arm for producing a permanent magnetic flux linking said core,said center arm having an arcuate outer surface, means to resilientlyurge said armature into abutting contact with said arcuate surface ofsaid center arm and to permit displacement of the armature from a givenposition towards either of said outer arms, said exciter coils beingoppositely acting and being disposed on said outer arms for magnetizingsaid outer arms in opposite directions to one another, and means forexciting said exciter coils from an alternating current electricitysupply whereby the magnitude of the excitation of the electromagneticsystem from the exciter coils is approximately equal to the magnitude ofthe premagnetization produced by said permanent magnet.

15. In a hair cutting machine, in combination, a housing unit; anelectromagnetic core unit arranged within said housing unit, one of saidunits having a guide face; an elongated armature having a portion with aface thereof superimposed on said guide face, at least one of Said facesbeing curved so that said elongated armature is adapted to carry out anoscillatory rolling movement on said guide face; and a bearing elementconsisting of resilient material and interposed between another face ofsaid portion of said elongated armature and one of said units andsupporting said portion of said elongated armature for damped movementin directions required during oscillatory rolling movement of saidarmature on said guide face.

References Cited in the le of this patent UNITED STATES PATENTS1,891,486 Wahl Dec. 20, 1932 1,895,292 Miner Ian. 24, 1933 2,063,116Nordhem Dec. 8, 1936 2,304,525 Andis Dec. 8, 1942 2,404,227 Hall July16, 1946 2,610,995 Orsatti Sept. 16, 1952 FOREIGN PATENTS 187,234Switzerland Jan. 16, 1937 436,717 Great Britain Oct. 17, 1935 887,698France Aug. 16, 1943

